Embodiments herein generally relate to printers and copiers or reproduction machines, and more particularly, concerns a system and method for aligning sheets within the media path and more particularly to embodiments that provide a prediction of the best lateral location for a movable registration carriage that depends upon the position of the next upcoming sheet.
Certain sheet registration devices within media paths of printers and copiers require part of the registration device, in this case the carriage which performs the cross-process direction movement, to correct for sheet lateral error. The carriage also undergoes a reset move back to some home position after it registers a sheet. This is normally done in the inter-document zone (IDZ) gap. One approach is to go back to the same reset position (nominal zero, or centered position) always, irrespective of the next sheet misalignment error. As a result, the carriage sometimes must travel a large distance to correct for worst case errors in either direction of the nominal.
The embodiments herein provide a sensing system and a method that enables the computation of a location to which the carriage is positioned in the cross-process (lateral) direction before the sheet enters the carriage. The sensing system measures the lateral error of the upcoming sheet and computes the appropriate pre-position location for the carriage that minimizes carriage movement. The carriage control system then moves the carriage to that location. This reduces the range of total carriage motion significantly.
More specifically, embodiments herein feed sheets through a media path in a process direction and move a laterally movable sheet registration carriage (positioned within the media path) in a lateral direction perpendicular to the process direction. The embodiments herein determine the error of the sheets within the media path before the sheets enter the sheet registration carriage, using first sensors positioned within the media path. This allows the embodiments herein to move the sheet registration carriage to a variable lateral starting position (as opposed to a consistent reset position or centered reset position) before the sheets enter the sheet registration carriage based on the error of the sheets as determined by the first sensors. The error can be the amount of lateral error, or simply can be a classification of lateral error (right error, left error, etc.).
Once the sheets enter the sheet registration carriage, the embodiments herein determine the amount of misalignment of the sheets using second sensors positioned within the sheet registration carriage. This allows the embodiments herein to align the sheets to a predetermined lateral position within the media path based on the amount of the misalignment, using the sheet registration carriage.
While the sheet registration carriage is commonly reset to the center position (or other consistent lateral reset position); the embodiments herein do not reset the sheet registration carriage to a consistent lateral reset position. Instead, the embodiments herein move the sheet registration carriage to a variable starting position that is different than the center of the media path. The variable starting position is thus different than the normal lateral reset location of the sheet registration carriage. The variable lateral starting position comprises an anticipated carriage location that minimizes lateral range of the sheet registration carriage and maximizes effectiveness of sheet alignment operations of the sheet registration carriage.
System embodiments herein utilize a media path feeding sheets in a process direction and a laterally movable sheet registration carriage positioned within the media path. The sheet registration carriage is movable in a lateral direction perpendicular to the process direction. The system also includes first sensors positioned within the media path. The first sensors are operatively connected to the sheet registration carriage. The first sensors determine the error of the sheets within the media path before the sheets enter the sheet registration carriage.
The sheet registration carriage moves to a variable lateral starting position before the sheets enter the sheet registration carriage based on the error of the sheets as determined by the first sensors. Again, the error can comprise the amount of lateral error or simply the classification of lateral error.
Further, the system includes second sensors adjacent to the sheet registration carriage. The second sensors are operatively connected to the sheet registration carriage. The second sensors determine the amount of misalignment of sheets within the sheet registration carriage. The sheet registration carriage aligns the sheets to a predetermined lateral position within the media path based on the amount of the misalignment.
Some embodiments herein can be more complex and can precisely move the carriage to any specific lateral position along the full movement range of the carriage. For example, the sensors can provide a very detailed report of the exact lateral distance of misalignment of the next upcoming sheet. These sophisticated embodiments move the carriage to a more precise location depending upon the lateral distance measurement produced by the sensors.
Other embodiments can be more simplified (and more cost effective) and can more simply pre-position the carriage in just a limited number of preset positions depending upon the classification of a lateral error. For example, the classification can be as simple as whether or not there is a lateral error (of sufficient magnitude). In such embodiments, the sensors can simply report whether the sheet lateral position is greater or less than some predetermined misalignment level (e.g., plus or minus one-half the maximum lateral position error relative to nominal). If the predetermined misalignment level is not exceeded, such a simplified system will reset the carriage to the center position. To the contrary if the predetermined misalignment level is exceeded, these more simplified embodiments reset the carriage to a one-half the maximum offset from center (in the misalignment direction).
These and other features are described in, or are apparent from, the following detailed description.